This application relates to the art of ball valves and, more particularly, to a physical configuration of a valve ball that minimizes fluid pressure forces tending to rotate the ball when it is partly open. Although the invention will be shown and described with reference to a ball valve that has two seals, it will be appreciated that the improvements can be used in ball valves that have one seal.
Ball valves are used to control or throttle flow rates by adjusting the valve ball to a partly closed position. Fluid pressure acting on the valve ball tends to rotate the valve ball out of its desired position and undesirably change the flow rate. Therefore, braking or locking mechanisms are required to positively hold the valve ball in a desired position for maintaining a substantially constant throttled flow rate. These mechanisms may include manually engaged locks, braking mechanisms that are engaged by movement of the valve ball without an input to the adjustment handle, or adjustment mechanisms that provide inherent braking action such as a worm gear drive. Minimizing the fluid pressure forces that tend to move the valve ball from its desired position would make it possible to simplify or eliminate the locking or braking mechanisms.